Let's try using the formula for a chord and the formula

chord length is given by

Arc length is given by

Clyde is catching up to CeCe, so their distance along the arc is decreasing at -0.4 m/sec.

That is ds/dt = -.4.

. dr/dt is 0 because the radius does not change.

When they are 82 feet apart along the chord, then using

So, let's differentiate implicitly our chord formula.

The distance between them is decreasing at .229 m/sec.

Let's see if anyone concurs. Check my work.